Full-bridge resonant converter with hybrid control for wide input voltage range applications

Abstract

This paper proposes a hybrid control strategy for a full-bridge resonant converter. In the applications with a wide input voltage, a resonant converter with variable frequency control (VFC) has to modulate the converter operating in a wide switching frequency range to satisfy gain requirements, which results in some problems such as difficulty in optimizing the design of magnetic components, increased power loss and deteriorated electromagnetic interference. By use of VFC, primary-side phase shift control and secondary-side phase shift control, the frequency variable range can be greatly reduced and the conversion efficiency can be increased, which make the converter appropriate for a wide input voltage range. With this hybrid control strategy, the converter can automatically convert to the corresponding control mode according to variations of the input voltage and load, which has a good transient performance. The working principle, gain characteristics and design considerations of a hybrid controlled CLL resonant converter are introduced in detail. Experimental results are shown to demonstrate its validity and feasibility.